Effect of 12-week Practice of Anulom Vilom Pranayama as Adjunctive Therapy on the Cardiac Autonomic Balance, Cognition, Psychological Status, and Quality of Life in Individuals with Mild-to-Moderate Parkinson’s Disease: A Randomized Controlled Trial

Abstract

Context:

Patients with Parkinson’s disease (PD) commonly experience cardiac autonomic dysfunction, cognitive impairment, and psychological disturbances. Limitations in current treatment modalities warrant the need for simple, cost-effective adjuvant therapies. Pranayama, a fundamental component of yoga, has been proven to be beneficial for several medical disorders.

Aim:

This study aimed to assess the effects of the 12-week practice of Anulom Vilom Pranayama (AVP) or Alternate Nostril Breathing (ANB) as an adjunctive therapy on the cardiac autonomic balance, cognition, psychological status, and quality of life (QoL) in individuals with PD.

Subjects and Methods:

This randomized controlled trial involved 86 individuals (55 males, 31 females, aged 35–70 years) with mild-to-moderate PD. Participants were randomized into the control group receiving conventional treatment only or the test group receiving AVP as an adjunctive therapy to the conventional treatment. Cardiac autonomic status (heart rate variability [HRV]), cognition (P300, Reaction Time), affect, psychological status, and QoL were assessed in all the participants at baseline and after 12 weeks of respective intervention.

Statistical Analysis:

The change in study parameters (0–12 weeks) was compared between the control and test groups using the Mann–Whitney U test or Independent samples t-test. The correlation between the change in low-frequency (LF)/high-frequency (HF) ratio and QoL and its effect at 12 weeks was assessed using the Spearman correlation coefficient test. P < 0.05 was considered statistically significant.

Results:

The test group revealed significantly high total HRV (standard deviation of normal-to-normal intervals [SDNN], total power) and HRV indices of cardiac parasympathetic activity (square root of the mean of the sum of the squares of differences between adjacent NN intervals [RMSSD], percentage of NN50 [pNN50], HF power, HF normalized unit) and significantly low HRV indices of cardiac sympathetic activity (LF normalized unit) and cardiac sympathovagal balance (LF/HF ratio) compared to the control group. Similarly, significant improvement in cognition, psychological status, and QoL was also observed in the test group. While significant correlations were observed between the change in LF/HF ratio and QoL in both the groups, a significant correlation between the change in LF/HF ratio and positive affect was observed only in the test group.

Conclusions:

Twelve weeks of practice of AVP significantly improved the cardiac sympathovagal balance, cognition, positive affect, and QoL and decreased the negative affect, depression, stress, and anxiety in patients with mild-to-moderate PD.

Introduction

Parkinson’s disease (PD), a neurodegenerative disorder that affects the dopaminergic neurons in the basal ganglia (substantia nigra), is characterized by cytoplasmic spherical inclusions containing alpha-synuclein in the brain cells, which spread to neocortical and cortical regions as the disease progresses.[1]

Autonomic dysfunction affecting both sympathetic and parasympathetic nervous systems has been reported in patients with PD, a potential risk factor for increased risk of cardiovascular morbidity and mortality in these individuals.[2] However, despite its high prevalence, autonomic dysfunction is frequently underdiagnosed in patients with PD. Numerous studies have also reported a significant decline in cognition with feelings of distraction, impairment in memory, abstract thinking, and decision-making in PD patients. In addition, depression and anxiety are the other most common comorbidities in these individuals, leading to poor QoL.[3] Recent evidence suggests inflammation and oxidative stress as potential contributors to the degeneration of dopaminergic neurons in PD.[4] Homocysteine (HCY), a potential risk factor for cardiovascular disease and 8-hydroxy-2’-deoxyguanosine (8-OHdG), an important marker of oxidative DNA damage and disease progression, are known to be elevated in PD.[5]

To date, pharmacotherapy remains the first-line treatment for PD. Adjunctive therapies like deep brain stimulation and manipulative therapies such as chiropractic, physiotherapy, etc., often face limitations such as adverse effects, limited availability of field experts, the cost involved, accessibility, and feasibility.

Pranayama, or yogic breathing, an essential component of yoga, promotes an individual’s physical, mental, and emotional well-being by regulating the hypothalamic–pituitary–adrenal axis and the autonomic nervous system. Anulom Vilom Pranayama (AVP), also known as alternate nostril breathing (ANB), is a simple slow pranayama known to improve cardiac autonomic balance and overall cardiac function.[6] Regular practice of this pranayama is also known to improve cognitive functioning and general well-being.[7] However, the beneficial effects of AVP have not been studied in PD. Hence, this study aimed to assess the effect of 12 weeks of practice of AVP on cardiac autonomic balance, cognition, psychological status, and quality of life (QoL) in patients with PD.

Subjects and Methods

This study was carried out in the department of physiology in collaboration with the departments of neurology and biochemistry at a tertiary care medical college and hospital after getting approval from the institutional ethics committee for interventional studies (JIP/IEC/2022/030). Clinical Trial Registration was done before initiating the study (CTRI/2023/01/049251). The study protocol conformed to the ethical guidelines of the Declaration of Helsinki. The study details were explained, and written informed consent was obtained from all the study participants.

Sample size calculation

The sample size was estimated with a minimum expected difference in low-frequency power (LF): high-frequency power (HF) between the groups at the 12-week assessment as 1[8] with a standard deviation (SD) of 1.5 at 5% level of significance and 80% power. Considering a 15% drop-out, 43 individuals were included in each group.

The participants were recruited as per the following inclusion and exclusion criteria [Figure 1]:

Figure 1.

CONSORT diagram

Inclusion criteria

Patients, both males and females, aged 30–70 years, with clinically diagnosed idiopathic parkinsonism with “Movement Disorder Society-Sponsored Revision of the Unified PD Rating Scale (MDS-UPDRS)” motor score <59 and Hoehn–Yahr staging score ≤2, who were all on stable anti-Parkinsonian therapy for the past 3 months were recruited in the study.

Exclusion criteria

Individuals with poorly controlled chronic cardiovascular or respiratory comorbidities, advanced dementia, unstable medical illnesses, current active infections such as tuberculosis or COVID-19, comorbid autoimmune diseases, malignancies, preexisting endocrine, hepatic, renal, and connective tissue disorders, and those who were already practicing some form of structured pranayama or yoga on a regular basis were excluded from the study.

Study design

This study involves randomized controlled trial.

Randomization

Block randomization using computer-generated random numbers with varying blocks was followed for randomization.

Allocation concealment was ensured using serially numbered opaque sealed envelopes (SNOSE).

The eligible participants were randomized to receive AVP as adjunctive therapy to conventional treatment (test group) or conventional treatment only (control group).

Blinding was not implemented in this study because the nature of the intervention necessitated active participant involvement, making it impractical to conceal the treatment allocation.

Assessment of anthropometric and basal cardiovascular parameters

Participants were advised to report at the autonomic function testing laboratory in the Department of Physiology between 8 am and 11 am. The participants’ demographic data were noted and entered into a data sheet. Following standardized procedures,[9] the subjects’ height and weight were measured, and BMI was calculated using Quetelet’s formula, weight in Kg divided by the square of the height in meters.

Blood pressure was measured in sitting posture using an automated blood pressure monitor (Omron, HEM-8712, Omron Healthcare Co. Ltd, Kyoto, Japan). After 5 min of rest, two readings were taken at an interval of one minute, and the average of the two readings was taken as the subject’s blood pressure. Mean arterial pressure (MAP) and rate pressure product (RPP) were calculated, and basal heart rate was noted from the BP apparatus.

MAP = Diastolic blood pressure + 1/3 (Systolic blood pressure – Diastolic blood pressure)

RPP = Heart rate × Systolic blood pressure × 10⁻²

Assessment of cardiac autonomic activity and balance

Assessment of cardiac sympathetic and parasympathetic activity by heart rate variability (HRV) technique was done as per the “Guidelines of the Taskforce of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology”[10] using the BIOPAC MP 150 (Biopac Systems Inc., Goleta, California, United States) data acquisition system. The subjects were asked to rest for 15 min in the supine position (room temperature 24° Celsius), following which lead II ECG was recorded at the rate of 1000 samples per second for 5 min. From this ECG data, R-R intervals were computed and entered into the Kubios software version 3.5 (Kubios Oy, Kuopio, Finland) for computing HRV indices indicative of both sympathetic and parasympathetic activity. Frequency domain indices, namely “total power (TP), LF power (LF power), LF component expressed as normalized unit (LFnu), HF power (HF power), HF component expressed as normalized unit (HFnu), the ratio of LF to HF power (LF/HF ratio) and time-domain indices namely square root of the mean squared differences of successive normal-to-normal RR intervals (RMSSD), the SD of normal to normal RR interval (SD of normal-to-normal intervals [SDNN])”, the number of interval differences of successive normal to normal RR (NN) intervals greater than 50 ms (NN50), and the proportion derived by dividing NN50 by the total number of NN intervals (pNN50) were considered for analysis.

Assessment of cognition

Recording of P300 event-related potential

The event-related potential P300 was recorded using the Nihon Kohden Electrophysiology/Electromyography (EP/EMG) machine as per the recommendation of the “International Federation of Clinical Neurophysiology.”[11] The participants were instructed to come with a clean, oil-free scalp, and ear wax was ruled out before the recording. Ground (Fz), active (Cz), and reference electrodes were placed at the forehead, vertex, and on both mastoids, respectively. P300 was recorded in the context of a standard auditory oddball paradigm. The participants were instructed to detect target or rare stimuli (tone burst) within a series of nontarget or frequent stimuli (click). The percentage of rare stimuli was set at 20% and frequent stimuli at 80% with a stimulation rate of 0.5 Hz/s. The stimuli were delivered via headphones binaurally with 40 dB sound pressure level intensity. The bandpass filter range was kept at 0.1 Hz and 50 Hz. The P300 is a positive deflection elicited in response to an Oddball paradigm, where the subject identifies the occasional stimuli (target stimuli). The signals were picked up by electrodes and filtered, amplified, averaged, displayed, and analyzed using Neuropack software on the Nihon Khoden EP/EMG machine screen. The recording procedure was repeated for the reproducibility of P300, and the markings were done for the latencies of N1 (negative wave at 100 ms), P2 (positive wave at 200 ms), N2 (negative wave at 200 ms), and P300 (positive wave at 300 ms) in milliseconds and amplitudes of N1-P2, P2-N2, and N2-P3 in microvolts. However, P300 latency in milliseconds and N2-P3 amplitude in microvolts were considered for analysis.

Assessment of auditory and visual reaction time

Reaction time, a measure of an individual’s sensorimotor performance and alertness, was assessed for auditory and visual stimuli. Participants were asked to sit comfortably on a stool. Auditory reaction time was recorded for low and HF sounds and visual reaction time for red and green light. As soon as the individual perceived the stimulus, they were asked to press the response switch. The quickness with which they performed was obtained from the display of the instrument in milliseconds, which was a measure of their reaction time. After familiarizing the subjects with the procedure, three sets of recordings were taken, and the average was calculated.

Assessment of psychological status

Assessment of affect

The affect of the study participants was assessed using the PANAS-SF (Positive and Negative Affect Schedule-Short Form), a 20-item self-reported questionnaire with 10 questions inquiring about positive affect and 10 questions inquiring about negative affect. The items were rated on a 5-point Likert scale, with higher scores indicating high positive or negative affect.[12]

Assessment of depression, anxiety, and stress

Depression, anxiety, and stress levels of the study participants were assessed using DASS-21 (Depression, Anxiety and Stress Scale), a self-reported questionnaire with items rated on a 4-point Likert scale ranging from “0” (does not apply to me) to “3” (applies to me most of the time). The scores were summed up in each subscale and categorized into mild, moderate, severe, and extremely severe based on standard guidelines.[13]

Assessment of quality of life

The QoL of the study participants was assessed using the WHO-QoL-Bref questionnaire (World Health Organization QoL -Brief), a 26-item instrument that assesses QoL in four domains: physical health, psychological health, social relationships, and environmental health. Higher scores indicate a higher QoL.[14]

Assessment of biochemical parameters

Five ml of venous blood was withdrawn from the study participants, and the biochemical parameters, namely serum HCY and serum 8-OHdG, were estimated using the ELISA (Enzyme-Linked Immunosorbent Assay) technique.

Administration of anulom vilom pranayama

AVP was taught to test group participants at the Advanced Centre for Yoga Therapy and Research (ACYTER) at the Institute. The training was given for 15 min once a month for 3 months under the supervision of a certified yoga trainer. For the remaining days, the participants were advised to practice AVP at home twice daily—once in the morning and once in the evening—for 15 minutes per session, under the supervision of a caregiver or a relative.

Description of anulom vilom pranayama

AVP involves breathing through the left and right nostrils alternately without holding the breath.[15,16] To perform this pranayama, the subjects were asked to sit in a comfortable position (sukhasana), keeping their head and spine straight and eyes closed. They were asked to take a few deep breaths to help them relax. The right thumb and right ring finger were used to occlude the nostrils. The subjects started by exhaling through the left nostril while closing the right nostril. Then, they inhaled through the left nostril. Next, they exhaled through the right nostril while closing the left nostril, then inhaled through the right nostril and exhaled through the left nostril. This completed one cycle of AVP.

The steps of AVP were handed over as a pamphlet to the test group participants. They were taught to perform the AVP to their capacity. The caregivers/relatives were asked to supervise and maintain a compliance diary to enter the patient’s daily practice. The same was cross-checked during the patient’s monthly visit to ACYTER. Periodic phone calls were also made to motivate the patients to practice the pranayama for 12 weeks and to follow their conventional therapy.

The control group individuals were advised through periodic phone calls to follow the prescribed conventional therapy and their routine follow-up visits to the neurology OPD.

Statistical analysis

Data entry was done using Epicollect and statistical analysis was done using IBM SPSS Statistics for Windows, Version 22.0. (Armonk, NY: IBM Corp). Both descriptive and inferential statistics were used to analyze the data. Baseline characteristics of the patients with mild-to-moderate PD are presented by descriptive statistics. The distribution of categorical variables, such as gender, is expressed in frequency and percentages. The normality of continuous data was assessed by the Kolmogorov–Smirnov test.

The continuous variables such as age, cardiac sympathovagal indices, cognition, affect score, DASS score, QoL, and serum levels of cardiovascular risk and oxidative stress marker are expressed as mean ± SD or median with interquartile range, depending on the distribution of the data. The change in study parameters (0 weeks minus 12 weeks) was compared between the control and test groups using the Mann–Whitney U test or Independent samples t-test. The correlation between the change in sympathovagal balance (LF/HF ratio) and QoL and its affect at 12 weeks was assessed using the Spearman correlation coefficient test. P < 0.05 was considered statistically significant.

Results

A total of 86 individuals aged between 35 and 70 years with mild-to-moderate PD were randomized into the control group (conventional treatment only) or the test group (AVP plus conventional therapy). There was no significant difference in the baseline anthropometric, clinical characteristics, and cardiovascular parameters between the groups [Table 1]. Similarly, comparison of baseline HRV, cognitive parameters, psychological parameters, QoL, and biomarkers showed no significant difference between the control and test groups [Tables 2 and 3]. Comparison of change (0–12 weeks) in cardiovascular parameters, HRV, and cognitive parameters between the groups revealed a significant increase in total HRV (Total Power), cardiac parasympathetic indices (HF power, HF nu), and measures of cognition (P300, reaction time); however, there was a significant decrease in cardiac sympathetic activity (LF nu) and sympathovagal balance (LF/HF) in the test group compared to the control group [Table 4]. Comparison of change (0 weeks minus 12 weeks) in psychological status, QoL, and biomarkers between the groups revealed a significant decrease in depression, anxiety, stress levels, negative affect, and serum HCY and serum 8-OHdG and improved QoL domains in the test group compared to the control group [Table 5]. Significant negative correlations were observed between LF/HF ratio, QoL, and positive affect in the test group [Table 6]. After 12 weeks of intervention, significant differences in heart rate variability and cognitive parameters were observed between the control and test groups [Supplementary Table 1]. Similarly, psychological parameters, quality of life, and biomarker levels also differed significantly between the groups [Supplementary Table 2].

Table 1.

Comparison of baseline anthropometric, clinical characteristics, and cardiovascular parameters between the groups

Parameters		Control group (n=43)		Test group (n=43)		P
Age (years)*		56.65±9.94		57.65±7.60		0.602
Male, n (%)a		31 (72.1)		24 (55.8)		0.177
Female, n (%)a		12 (27.9)		19 (44.2)
BMI (kg/m2)*		25.50±1.78		25.52±2.72		0.975
UPDRS score**		50 (38–52)		46 (41–50)		0.29
Disease duration (years)**		6 (2–7)		4 (3–7)		0.234
HR (bpm)*		71.23±9.39		74.67±12.73		0.15
SBP (mmHg)*		123±18		128±13		0.239
DBP (mmHg)*		81±7.9		81±10		0.991
MAP (mmHg)*		95.8±7.8		97.2±10.3		0.480
RPP (mmHg)*		92±16.1		99.7±20.9		0.05

Values are expressed as *Mean±SD-independent samples t-test, **Median (IQR)-Mann–Whitney U-test, ^aPercentage. P<0.05 was considered statistically significant. SD: Standard deviation, BMI: Body mass index, UPDRS: Unified Parkinson’s Disease Rating Scale, SBP: Systolic blood pressure, DBP: Diastolic blood pressure, PP: Pulse pressure, MAP: Mean arterial pressure, RPP: Rate pressure product, HR (bpm): Heart rate (beats/min), IQR: Interquartile range

Table 2.

Comparison of baseline heart rate variability and cognitive parameters between the groups

Parameters		Control group (n=43)		Test group (n=43)		P
Mean RR (ms)		810 (746–846)		779 (732–906)		0.75
Time domain indices of HRV
SDNN (ms)		14.6 (9.6–115.3)		34.1 (14.2–41.2)		0.65
RMSSD (ms)		14.6 (9.6–115.3)		34.1 (14.2–41.2)		0.25
pNN50 (%)		4 (0.67–14.67)		8.33 (2.67–15.33)		0.14
Frequency domain indices of HRV
LF (ms2)		116 (99–405)		120 (102–415)		0.54
HF (ms2)		39 (28–118)		42 (31–124)		0.27
LF:HF		3.46 (3.22–3.91)		3.25 (2.76–3.72)		0.11
TP (ms2)		163 (134–576)		169 (140–595)		0.27
LF nu		77.61 (76.32–79.66)		76.52 (73.42–78.85)		0.11
HF nu		22.39 (20.34–23.68)		23.48 (21.15–26.17)		0.12
Cognition parameters
Event-related potential (P300)
P300 latency (ms)		385 (314–448)		362 (345–380)		0.063
P300 amplitude (µV)		0.82 (0.33–1.47)		1.09 (0.79–1.33)		0.258
Auditory reaction time
Click (ms)		0.28 (0.2–0.32)		0.28 (0.26–0.29)		0.866
Tone (ms)*		0.29±0.06		0.3±0.07		0.5
Visual reaction time
Red light (ms)*		0.48±0.06		0.45±0.08		0.09
Green light (ms)		0.28 (0.2–0.32)		0.28 (0.26–0.29)		0.866

*Values are expressed as mean±SD-independent samples t-test, P<0.05 was considered statistically significant. Values are expressed as median (IQR). Mann–Whitney U-test-P. P<0.05 was considered statistically significant. IQR: Interquartile range, SD: Standard deviation, Mean R–R: Mean duration of R–R interval, Mean HR: Mean heart rate, SDNN: SD of normal-to-normal intervals, RMSSD: Square root of the mean of the sum of the squares of differences between adjacent NN intervals, pNN50 (%): Percentage of NN50 count divided by the total number of all NN intervals, LF power: Low-frequency power, HF power: High-frequency power, LF/HF: Low-frequency to high-frequency ratio, TP: Total power, LF nu: Low-frequency normalized unit, HF nu: High-frequency normalized unit

Table 3.

Comparison of baseline psychological parameters, quality of life, and biomarkers between the groups

Parameters		Control group (n=43)		Test group (n=43)		P
Psychological parameters
PANAS positive affect scores		11 (10–16)		11 (10–15)		0.402
PANAS negative affect scores		38 (26–40)		36 (34–40)		0.456
Depression scores		16 (12–18)		16 (14–20)		0.906
Anxiety scores		12 (8–14)		12 (10–14)		0.424
Stress scores		20 (10–22)		14 (12–22)		0.819
Quality of life (WHO-QoL-Bref)
Physical domain		19 (17–40)		36 (18–36)		0.694
Psychological domain		19 (17–25)		25 (19–25)		0.117
Social domain		5 (3–12)		8 (4–12)		0.221
Environmental domain		12 (10–30)		16 (14–20)		0.09
Biomarkers
s-HCY		827.84 (604.14–880.07)		822.63 (576.44–1582.65)		0.598
s-8OHdG		30.91 (22.83–97.27)		56.73 (26.58–142.85)		0.209

Values are expressed as median (IQR), Mann–Whitney U-test-P. P<0.05 was considered statistically significant. PANAS-SF: Positive affect and negative affect score-short form, WHO-QoL-Bref: World Health Organization-Quality of Life-Brief Questionnaire, HCY: Homocysteine, 8-OHdG: 8-hydroxy-2-deoxy guanosine, IQR: Interquartile range

Table 4.

Comparison of change in cardiovascular, heart rate variability, and cognitive parameters between the groups (0 weeks minus 12 weeks)

Parameters		Control group (n=43)		Test group (n=43)		P
SBP (mmHg)		−1 (−2–1)		2 (1–11)		<0.05
DBP (mmHg)		−2 (−2–0)		−2 (−5–3)		0.628
MAP (mmHg)		−1 (−2.3–0.6)		1.6 (−2.3–4.3)		<0.05
RPP (mmHg)		−0.28 (−3.5–1.6)		3.4 (−1.9–14.8)		<0.05
Heart rate variability parameters
Mean RR (ms)		1 (−2–2)		−2 (−48–2)		<0.05
Mean HR (bpm)		−3 (−14–4)		−2 (−8–4)		0.387
Time domain indices of HRV
SDNN (ms)		0.9 (−0.7–3.5)		−26.4 (−63.8–−10.7)		<0.05
RMSSD (ms)		1.9 (−0.8–8.6)		−43.6 (−76.1–−19.9)		<0.05
pNN50 (%)		0.44 (−0.2–3.69)		−5.96 (−11.75–−3.20)		<0.05
Frequency domain indices of HRV
LF (ms2)		−3 (−6–−1)		−70 (−368–−17)		<0.05
HF (ms2)		−3 (−4–−3)		−178 (−261–−32)		<0.05
LF:HF**		0.19±0.22		1.43±1.03		<0.05
TP (ms2)		−7 (−16–−4)		−216 (−651–−71)		<0.05
LF nu		0.8 (0.34–1.7)		13.19 (3.41–18.74)		<0.05
HF nu		−0.8 (−1.71–−0.8)		−13.50 (−18.74–−4.23)		<0.05
Cognitive parameters
Event-related potential (P300)
P300 latency (ms)**		−14.67±43.36		53.28±36.91		<0.05
P300 amplitude (µV)**		0.03±0.11		−0.15±0.10		<0.05
Auditory reaction time
Click (ms)**		−0.07±0.11		0.04±0.04		<0.05
Tone (ms)**		−0.06±0.07		0.10±0.06		<0.05
Visual reaction time
Red light (ms)**		−0.01±0.05		0.05±0.05		<0.05
Green light (ms)		−0.004 (−0.03–0.008)		0.39 (0.019–0.066)		<0.05

**Values are expressed in mean±SD, independent samples t-test. Values are expressed as median (IQR), Mann–Whitney U-test-P. P<0.05 was considered statistically significant. P<0.05 was considered statistically significant. Mean R–R: Mean duration of R–R interval, Mean HR: Mean heart rate, IQR: Interquartile range, SD: Standard deviation, SDNN: SD of normal-to-normal intervals, RMSSD: Square root of the mean of the sum of the squares of differences between adjacent NN intervals, pNN50 (%): Percentage of NN50 count divided by the total number of all NN intervals, LF power: Low-frequency power, HF power: High-frequency power, LF/HF: Low-frequency to high-frequency ratio, TP: Total power, LF nu: Low-frequency normalized unit, HF nu: High-frequency normalized unit

Table 5.

Comparison of change in psychological parameters, quality of life, and biomarkers between the groups (0 weeks minus 12 weeks)

Parameters		Control group (n=43)		Test group (n=43)		P
Psychological parameters
PANAS positive affect scores**		2.721±1.2017		−11.977±7.664		<0.05
PANAS negative affect scores		−4 (−6–−2)		16 (12–18)		<0.05
Depression scores		0.00 (0–2)		2.00 (2–2)		<0.05
Anxiety scores		−2 (−2–0)		2.00 (2–2)		<0.05
Stress scores		−2 (−2–0)		2.00 (2–2)		<0.05
Quality of life (WHO-QoL-Bref)
Physical domain		4 (7–0)		−2 (−2–−4)		<0.05
Psychological domain		3 (4–0)		0 (0–−2)		<0.05
Social domain		0 (2–0)		−2 (−1–3)		<0.05
Environmental domain		12 (30–10)		−2 (0–−6)		<0.05
Biomarkers
s-HCY		−116.539 (−370.69–216.30)		518.93 (253.05–988.23)		<0.05
s-8OHdG		−6.93 (−32.34–−0.37)		36.49 (10.97–127.78)		<0.05

**Values are expressed as mean±SD. P<0.05 was considered statistically significant. Values are expressed as median (IQR), Mann–Whitney U-test-P. PANAS-SF: Positive affect and negative affect score-short form, DASS-21: Depression Anxiety Stress Scale-21 Questionnaire, WHO-QoL-Bref: World Health Organization-Quality of Life-Brief Questionnaire, HCY: Homocysteine, 8-OHdG: 8-hydroxy 2-deoxy guanosine, IQR: Interquartile range, SD: Standard deviation

Table 6.

Correlation between change (0 weeks minus 12 weeks) in low-frequency/high-frequency and change in quality of life and positive affect and negative affect score – short form questionnaire in test and control groups

Variable		Groups		Correlation coefficient		Statistical significance
WHO-QoL-Bref		Control group		−0.34		0.024*
		Test group		−0.40		0.001*
PANAS-SF positive affect		Control group		0.089		0.571
PANAS-SF negative affect				0.150		0.336
PANAS-SF positive affect		Test group		−0.460		0.002*
PANAS-SF negative affect				0.014		0.928

Values are Spearman’s rank correlation coefficient. *P<0.05 was considered statistically significant. WHO-QoL-Bref: World Health Organization-Quality of Life-Brief Questionnaire, PANAS-SF: Positive Affect and Negative Affect Score-Short Form Questionnaire

Supplementary Table 1.

Comparison of heart rate variability and cognitive parameters between the groups after 12 weeks of intervention

Parameters		Control group (n=43)		Test group (n=43)		P
Mean RR (ms)		812 (734–846)		892 (742–992)		<0.05
Time domain indices of HRV
SDNN (ms)		13.5 (9.5–101.6)		64.8 (47.2–112.7)		<0.05
RMSSD (ms)		12.9 (8.5–102.5)		99.6 (42.6–118.5)		<0.05
pNN50 (%)		4.76 (0–9.6)		15.2 (11.56–33.93)		<0.05
Frequency domain indices of HRV
LF (ms2)		120 (102–415)		468 (168–488)		<0.05
HF (ms2)		42 (31–124)		288 (64–322)		<0.05
LF:HF		3.26 (2.76–3.73)		1.63 (1.47–2.52)		<0.05
TP (ms2)		169 (140–595)		774 (248–817)		<0.05
LF nu		76.52 (73.42–78.85)		61.90 (59.54–71.60)		<0.05
HF nu		23.48 (21.15–26.17)		38.10 (28.40–40.46)		<0.05
Cognition parameters
Event-related potential (P300)
P300 latency (ms)		410 (354–448)		303 (301–321)		<0.05
P300 amplitude (µV)		0.82 (0.32–1.45)		1.35 (0.99–1.45)		<0.05
Auditory reaction time
Click (ms)		0.37 (0.27–0.39)		0.25 (0.24–0.27)		<0.05
Tone (ms)*		0.39 (0.29–0.40)		0.20 (0.18–0.22)		<0.05
Visual reaction time
Red light (ms)*		0.50 (0.42–0.53)		0.40 (0.35–0.47)		<0.05
Green light (ms)		0.48 (0.36–0.50)		0.39 (0.32–0.43)		<0.05

*Values are expressed as mean±SD-independent samples t-test, P<0.05 was considered statistically significant. Values are expressed as median (IQR). Mann–Whitney U-test-P. P<0.05 was considered statistically significant. SD: Standard deviation, Mean R–R: Mean duration of R–R interval, Mean HR: Mean heart rate, SDNN: SD of normal-to-normal intervals, RMSSD: Square root of the mean of the sum of the squares of differences between adjacent NN intervals, pNN50 (%): Percentage of NN50 count divided by the total number of all NN intervals, LF power: Low-frequency power, HF power: High-frequency power, LF/HF: Low-frequency to high-frequency ratio, TP: Total power, LF nu: Low-frequency normalized units, HF nu: High-frequency normalized units, IQR: Interquartile range

Supplementary Table 2.

Comparison of psychological parameters, quality of life, and biomarkers between the groups after 12 weeks of intervention

Parameters		Control group (n=43)		Test group (n=43)		P
Psychological parameters
PANAS positive affect scores		8 (6–14)		24 (18–32)		<0.05
PANAS negative affect scores		40 (32–42)		22 (18–22)		<0.05
Depression scores		16 (12–18)		14 (12–18)		<0.05
Anxiety scores		12 (12–14)		10 (8–12)		<0.05
Stress scores		20 (14–24)		12 (10–20)		<0.05
Quality of life (WHO-QoL-Bref)
Physical domain		11 (10–36)		38 (20–40)		<0.05
Psychological domain		14 (10–25)		25 (20–27)		<0.05
Social domain		5 (3–10)		10 (9–13)		<0.05
Environmental domain		10 (10–28)		20 (16–26)		<0.05
Biomarkers
s-HCY		863.22 (584.72–1100.48)		343.17 (154.89–622.23)		<0.05
s-8OHdG		55.82 (23.06–125.09)		10.46 (8.45–15.07)		<0.05

Values are expressed as median (IQR), Mann–Whitney U-test-P. P<0.05 was considered statistically significant. PANAS-SF: Positive affect and negative affect score-short form, DASS-21: Depression Anxiety Stress Scale-21 Questionnaire, WHO-QoL-Bref: World Health Organization-Quality of Life-Brief Questionnaire, HCY: Homocysteine, 8-OHdG: 8-hydroxy 2-deoxy guanosine, IQR: Interquartile range

Discussion

PD, one of the underdiagnosed disorders among the elderly, is associated with cardiovascular morbidities, cognitive decline, impairment in bodily functions, psychological disturbances, and poor QoL. In this study, 86 individuals aged 35–70 years diagnosed with mild-to-moderate PD, fulfilling the inclusion and exclusion criteria, were recruited. Participants were randomized to receive AVP therapy as adjunctive therapy (test group) or conventional treatment only (control group) for 12 weeks. The cardiac autonomic status, cognition, psychological status, QoL, and biochemical markers of cardiovascular disease and oxidative DNA damage were assessed at baseline (0 weeks) and at the end of 12 weeks in participants of both groups. The change (0 weeks–12 weeks) in the above-mentioned study parameters was compared between the test and control groups. At baseline, the study parameters were comparable between the groups.

Autonomic imbalance with increased sympathetic and decreased parasympathetic activity has been documented in previous studies in patients with PD,[6,7,17] and increased sympathetic activity is known to be associated with several cardiovascular disorders.[18,19] In this study, the cardiac sympathovagal balance (LF/HF) and cardiac sympathetic index (LF nu) decreased significantly while the cardiac parasympathetic indices (RMSSD, pNN50, HF power, HF nu) and total HRV (SDNN, Total Power) increased significantly at the end of 12 weeks in the test group which received AVP as adjunctive therapy compared to the control group which received conventional therapy alone.

ANB is a form of slow-paced deep breathing pranayama that is known to improve cardiac autonomic balance. It is believed that breathing through the right nostril activates the sympathetic nervous system while breathing through the left nostril activates the parasympathetic nervous system. Thus, AVP, also known as Alternative Nostril Breathing (ANB), brings in a balance between the sympathetic and parasympathetic nervous system,[20,21] which is disrupted in PD. The results of the cardiac autonomic function tests performed in this study reveal that individuals who received AVP in addition to conventional therapy had an improvement in their cardiac autonomic balance compared to those who received conventional therapy alone.

In 2016, Tokic et al. reported prolonged P300 latency and decreased P300 amplitude, indicating cognitive decline among PD patients.[22] Another study done by Xu et al. in 2022 reported similar findings and concluded that P300 may be used as a potential electrophysiological biomarker for early diagnosis of cognitive impairment in PD.[23] Similarly, in 2023, a study conducted by Rajendran et al. among Indian PD patients also revealed similar findings.[24]

In this study, the comparison of the change in cognition parameters revealed a significant reduction in the auditory and visual reaction times and P300 latency and a significant increase in P300 amplitude at the end of 12 weeks in the test group compared to the control group. It is known that the conscious concentration of each breath during pranayama improves self-awareness and self-regulation. Regular practice of pranayama promotes cortical and subcortical connections, thereby enhancing the communications between afferent and efferent pathways, leading to improved cognition, attention, and neuronal processing.[6,25,26] In addition, studies have reported that regular practice of breathing exercises inhibits the ascending reticular activating system and thereby enhances the neuronal information processing system and or blocks out distracting inputs.[27,28] These mechanisms could be the plausible reasons for the significant improvement in cognition observed in the test group participants who practiced AVP for 12 weeks.

Studies by Saadat et al. and Lee et al. concluded that increased psychological disability and worsening psychiatric symptoms, including suicidal ideation, are associated with disease progression in PD patients.[29,30] In this study, a significant reduction in depression, anxiety, stress, and negative affect and a significant improvement in positive affect and overall QoL was noted at the end of 12 weeks in PD patients of the test group compared to those in the control group. Previous studies have stated that concentrating on one’s breath helps de-stress by shifting focus away from worries and promoting parasympathetic activity over sympathetic activity.[31] This enhances relaxation and mindfulness, improves reciprocal connections between the central and peripheral nervous systems, helps cope with stress, and improves psychological and emotional well-being and overall QoL.[6,32,33] A significant improvement in the psychological status and QoL observed in the test group participants of this study could be attributed to their regular practice of AVP in addition to their conventional treatment.

HCY, a risk factor for heart and neurodegenerative diseases[34,35] is reported to be elevated in PD patients. Interestingly, the study by Fan et al. in 2020 concluded that an increased level of HCY is associated with disease progression and severity in PD.[36] Similarly, serum 8-OHdG, a sensitive biomarker of oxidative stress, is also reported to be elevated in patients with PD.[37] In this study, at the end of 12 weeks, a significant reduction in the serum levels of these biomarkers was observed in the test group compared to the control group.

AVP increases oxygen availability and nitric oxide production, leading to vasodilation, reduced systemic vascular resistance, and lower blood pressure, thereby enhancing cardiovascular health.[6] Thus, AVP would aid in reducing inflammation and oxidative stress. These mechanisms clearly explain the changes observed in the test group participants of this study with respect to their serum levels of HCY and 8-OHdG.

The significant negative correlations observed between the change in the sympathovagal balance and QoL (WHO-QoL-Bref) in both the test and control groups point towards the fact that improvement in cardiac autonomic status is associated with improvement in QoL irrespective of the interventions. However, a significant negative correlation was observed between the change in sympathovagal balance and positive affect only in the test group but not in the control group. This finding could be attributed to the beneficial effect of AVP as an adjunctive therapy to conventional treatment.

Conclusions

Twelve weeks of regular practice of AVP effectively improves the cardiac autonomic balance, cognition, psychological status, and QoL in individuals with mild-to-moderate PD.

Limitations

First, patients with severe PD were not included in the study; therefore, the results of the study cannot be generalized to this group of patients. Second, the motor functions of the study participants were not assessed. Third, the self-reported questionnaires could have imposed subjective bias to a certain extent. Finally, the lack of blinding is another limitation, as it could have introduced potential biases. Hence, future studies could address this limitation by incorporating blinding wherever feasible.

Future perspectives

AVP may be tried as an adjunctive therapy along with conventional therapy for patients with severe PD. Similarly, the effects of long-term benefits of AVP and other simple yoga therapies can be investigated for both motor and nonmotor symptoms of Parkinson’s patients.

Ethical statement

The study was approved by the institutional Ethics Committee of Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER), Puducherry (JIP/IEC/2022/030).

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Institutional Intramural Research Fund, Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER), Puducherry - 605006.